def f(n):
    if n <= 1:
        return 1
    else:
        return n * f(n - 1)


num = (input('正整数:'))
s = f(num)
print(num, '的阶乘是:', s)


def fibo(n):
    if n <= 2:
        return 1
    else:
        return fibo(n - 1) + fibo(n - 2)


print('斐波那契数列的第{}项为{}'.format(7, fibo(7)))

sum = lambda a, b, c: a + b + c
print(sum(1, 2, 3))

fun = lambda m: m ** 2
print(fun(5))
